Method of applying heat to the coverings of electrically conductive cores



Sept. 13, 1932. F. M. Porri-:Rv 1,876,745

METHOD OF APPLYING HEAT T0 THE COVERINGS- 0F ELECTRICALLY CONDUCTIVE'CORES Filed Aug. 26.. 1927 Patented Sept. 13,1 1932 TES PATENT OFFICEFRANK M. roman., or noma, NEW rdiff;IssIGNonToCnNERAL CABLE CORPORATION,

or Niiwyonx, N. Y A CORPORATION or NwuEas-EY METHognor `APPIATING, HEATfro THE COVERINGS 0F ELECTRICALLY ONDUCTIVE CORES l Application filedlAugust 26, 1927. Serial No. 215,627.

The present invention relates to improve- -ments in methods ofandapparatus for generating and applying heat to non-metallic substancesdisposed permanently or temporarily about a metallic core, the principalobject of the invention being to so generate the heat that it may'beapplied progressively from the inner to the outer surface of thenonmetallic substance which is to be acted upon in order to secure themaximum desirable ei'ect of heat upon said substance.

The invention will be described in connection with .a particularembodiment thereof and a few specific applications ofthe invention toproblems arising in the industrial arts willbe set forth, and it will beunderstood by those skilled in the art that. the described embodimentand applications of the inventionA are selected merely for pur- .posesof illustration, and further, that the invention is susceptible ofembodiments and applications other than those specifically set forth. 'A

In the heat treatment of the insulating coverings of electrical wiresand cables, such coverings comprisingv rubber in some instances andfibrous dielectric material or varynishes in other instances, for thepurpose of driving out'moisture or, particularly inthe case of rubberCompounds, for the purpose of vulcanizing the same, it'would bedesirable to generate the applied heat internally v.inf

. followed in the case of substances temporarily applied to a metalliccore and so shaped and disposed with relation to the core that othermethods of heating the core cannot be practicably employed.

The accompanying drawing shows by way of example the manner in which thepresent invention may be applied; the apparatus bef ing shown-diagrammatically in VFigure l;

Vany other suitable moisture-resistant maand typical assemblies which`may be heat treated in accordance with the invention being showninFigures' 2 to 4 inclusive.

Referring first to Figure 2 of the drawing, an insulated electricalCable A is shown progressively cut away to reveal its internal-construction. This cable comprises a metallic conductor 10 which may beof copper or other suitable metal possessing properties'of high4electrical conductivity and low resistance. Preferably this conductor ifof high Conductivity isprovided with a coating 11 of tin or a coating 12of zinc, or both, for purposes which will be later explained. Theconductor, including the coating if applied, is covered with a tube ofinsulating compound 13 made up largely of rubber. This compound may beapplied by any of several known methods more or less generally used. Theinsulating material 13 may be covered or protected by further wrappingsor coatlo ings and asurface braid 14.

Figure 3 of the `drawing illustrates-another type `of insulationcommonly applied to electrical conductors and comprising successivewrappings l5 of fibrous material such as paper tape, surrounded andprotected by a moisture-proof sheath 1.6 which may be ofV lead as inordinary lead covered cable, or of terial. e

In the structures shown in Figures 2 and 3 thefcores or metallicconductors 10 are permanently enclosed within the surround ing material.Figure 4 shows a structure to which the invention maybe applied and inwhich a temporary core is employed. In the case of a temporary Coreit ispreferable, for reasons which will later appear, to use a metal ofrelatively highresistance to an electrical Current and the core itself,if it is of a vprecialole. diameter, may be hollow. In

igure 4 a tubularcore 20 is shown and this core has a central bore 21. Alayer 22 of rubber or other material to be treated is applied in anysuitable manner upon the core and may be subjectedv to heaty treatmentin accordance with the present invention as hereinafter explained.

Reverting to the lstructure shown in Fig- 10o ure 2, it may happen undercertain condicircuit which is arranged in close proximity tions that thecovering 13 of rubber or rubto the conductor to be heated, is of assmall her compound may contain a certain amount diameter as possible anda very high freof solvent or moisture which it is desired to quencyalternating Icurrent in the order 0f remove. The removal thereof canbest be 10,000 cycles per second and u Ward is used. effected by theapplication of heat,

where it contactswith the metallic conducsecond by the employment, forexample, of a. tor, and from there progressively outward vacuum tubeoscillator. v.

so that the moisture is driven out tothe sur- The amount of inducedcurrent which may ,s

- race of the covering 13 and there dissipated. be set up in theconductor to be heated de- A(ir-other ii rous material prior to theappli- Again in connection with the structure pends partly upon theresistance of the mafirst to Known apparatus is available or theproduc-V the inner surface of the coating, that is, tion of a frequencyof one million cycles per shown in Figure 3 it may be desired tothorterial in Lwhich the induced current is estaboughly dr out thewrapping 15 of paper lished. The core of the structure shown in tFigures 2 and 3'is mainly of copper or some cation ofthe lead sheath 16or its equivalent other low resistance metal in order that the and thistoo may be Vmosteffectively accomsame may be an -efficient electricalconductor plishedin similar manner. Furthermore in when in use. the CaSeOf the Covering 13 0f the ConduCtOI' Vdu'cea sufficient current to heatthe conductor shown in Figure 2, or in the case of the covwhilepracticing Vthe present invention thereon ering 22 upon the core 2O inFigure 4, it may and accordingly the conductoris coated with be desiredto continue the application of tin or zinc or both, as previouslydescribed, heat a Sufficient time and n a SunlCient in order to providea path for the induced curamount to accomplish what is known as therents which will be more resistant thereto vulcanization of the rubberor rubber comthan the copper or like metalr and'therefore pound, andthis too may be effected by the contribute substantially to thegeneration of This rendersit diiicult to in generation of heat in thecore and its appliheat. The circumferential path of the in- CatlOIltlleI'GflOlIl Outward lillIOllgll lille I`llbduced Current is largelyupon the Surface 0f ber. In the case of thick walls of rubber or theconductor to bo heated and although tho rubber compound it may bedesirable t0 Supcoatings of tin and zinc provide a path of Plement theapphcatlon 0f he@ t0 the Outer greater resistance, thecurrent willneverthesurface of the wall by the application of heat less flow in thatpath booauso of its proximity to the inner surface as herein describedin to the windings of the primary con, A1- order to insure uniform'.-vulcanization thongh'tha heating of the Copper wir@ may throughout theWalL Y be possible without the coatings of tin or Now referring toFigure of the drawing, zinc or both, the generation of heat is greatly adiagrammatic representation of apparatus assisted and to a large extentrendered pracfor carrying out the invention W1ll be deticable by thecoating of some highly resistant Scrlbed- The, appafatu ShOWIl 111FIgllI'e 1 metal on the surface of the copper conductor. representsdlag'ammatlcauy an arrange* The core of the structure shown in Figurement by which an electrical current may be 4 boing a temporary oneemployed merely' induced IlIl 2. metalli() COIG SllCll aS the C011- forthe purpose 0f Supplying internal heat-v duetors l0 of Figures 2 and 3(or the core ing to its covering, and since it need not serve 20 ofFlgllre 4) 1n Order t0 enelilte heat as an electrical conductor, may bemade of a therein This result iS aCCOmP Shed by Cl'ematerial which isrelatively a poor conductor ating a magnetic e'ld in close proximity t 0.and which has a high resistance. It therethe conductors through theagency of a prifore may be heated directly without the apmary coil orcoils 25 in which an alternating `plication upon its surface of highresistance current of high frequency is Caused t0 flow. metallic'coatings and by-currents of lower The alternating magnetic field thusset up frequency than are employed with the strucwill induce currents inthe conductor placed ture shown in Figures 2 and 3. therein, f orexample in the conductor l() held It is to be understood that thisinvention or passed at proper speedthrough the inmay have furtherembodiments and is subterior of the primary coil or coils. Inasmuch'ject to various changes within the scope of as the invention isadaptednfgr use in conthe appended olaims ,nw

nection with electrical conducts of-rirdi- 'What I claim is: "m' narysize, as forinstance a No. 14 B. & Si

1. The method of manufacturing electricalgauge wire, and inasmuch as theinduced eddy currents or currents in the nature of eddy currents set upin this wire tend to flow in a path rou hly parallel to the path ofcurrent flow in the primary coil, thevpath of the induced current willbe very short, the maximum being the circumference of the conductor tobe heated. Consequently the primary cables of indefinite length whichcomprises, covering alcopper conductor with a complete 'thin surfacecoating of tin, covering the tin coating'with a complete thin surfacecoating of zinc, covering the coating of zinc with a relatively thickcomplete surface coating of rubber, and vulcanizing the rubber b passiing the completed cablecontinuously t ugh cal cables of indefinitelength and having an.

a closely overlying coil of definite length carrying high frequencyelectrical currents, whereby the conductor' is inductively heated by thecurrent passing through said coil and produces heating of the rubbercoating from its interior surface outward.

2. The method of manufacturing electrical cables of indefinite lengthwhich comprises, covering a copper-conductor with a complete surfacecoating of tin, covering the tin coat- 3. The method of manufacturingelectrical cables of indefinite length which comprises, covering acopper conductor with a complete surface coating of tin, covering thetin with a complete surface coating of rubber, and vulcanizing therubber by passing the completed cable continuously through a closelyoverlying coil ofdefinite length carrying high frequency electricalcurrents whereby the conductor is inductively heated by the currentpassing through said coil and produces heating of the rubber coatingfrom its interior surface outward.

`4. The method of manufacturing electricalA cables of indefinite lengthwhich comprises covering a conductor of relatively low resistance with acomplete thin surface coating of conducting material of relativelyhigher resistance, covering thel first mentioned coating with arelatively thick surface coating of rubber and vulcanizing the rubber bypassing the completed cable continuously through a closely overlyingcoil of definite length carrying high frequency lelectrical currentswhereby the conductor is inductively heated by thecurrent passingthrough said coil and produces heating of the rubber coating from itsinterior surfaceoutward. j A

5. The method of manufacturing electrielectrical conductor of lowresistance, whi'ch comprises, applying to the conductor an elementproviding a conducting path of relatively high resistance, enclosin theconductor with a covering of noncon ucting material andlheating thecovering' by passing the completed-cable through a closely overlyingcoil of definite length carrying high frequency electrical currentswhereby the conductor is inductively heated by the current passingthrough said coil and produces heating of the covering from itsinterionsurface outward.

6. The method of manufacturing electrical cables of indefinite lengthand having an electrical conductor of low resistance, which comprisesapplying to the conductor an element providing a Conducting path ofrelatively high resistance,enclosing the conductorwith a completecovering of insulating material and heating the-insulating material bypassingsuccessive lengths of the completed cable through a closelyoverlying coil of definite length carrying high frequency electricalcurrents, whereby the conductor is inductively heated by the currentspassing through said coil and produces heating of the covering from itsinterior surface outward.

7. The method of heating an electrically non-conductive material upon acore of highly conductive material which comprises covering the outersurface of the core with a relative poorer conductive material prior toapplication of the non-conductive material and heating the core byinduced effects of electrical currents of high frequency;

8. The method of manufacturing electrical cables ofv indefinite llengthwhich comprises, covering a copper conductor with a complete thinsurface coating of tin, covering the tin coating with a complete thinsurv face coating of zinc, covering the coating of' zinc with a completerelatively 'thick surface coating of non-conductive material and heatingthe same b passing the cable continuously through a clbsely overlyingcoil of definite length carrying high frequency electrical currents,whereby the conductor is inductively heated by the current passingthrough said coil and produces heating of the covering from its interiorsurfacev outward.

9. The method of manufacturing electrical cables of indefinite lengthwhichcomprises,

covering a copper conductor with a comf plete surface coating of tin,covering the tin coating-with -a complete surface coating of zinc,covering the coating of zinc with a complete surface coating of anon-conductive material and heating the same by passing the cable by acoil of definite length carrying high frequency electrical currents,whereby the. conductor is inductivelyheated by the I current passingthrough said coil and produces heating of the covering from its interiorsurface outward.v

10. The method of manufacturing electrical cables of indefinite lengthwhich comprises covering a conductor of relatively low resistance with asurface coating of conducting material of relatively higher resistance,covering the first mentioned coating with a. coating of non-conductivematerial, and

kheating the same by Acarrying the cablepast a closely adjacentcoil ofdefinite length carrying high frequency electrical currents whereby theconductoris inductively heated by the current passing through said coiland produces'heating of the insulating covering from its interiorsurface outward.

11. The method of heating a substantially electrically.non-conductiveelement u on a core comprising an inner element of re atively highlyconductive material and an outer element of relatively poorerconductive-material which comprlses heating the core by inducedeffectsof electrical currents, whereby the non-conductive element is heatedfrom its interior surface outwardly.

l2. The methodof heating a substantially electrically non-conductiveelement upona core of relatively highly conductive material whichcomprises applying to the outer surface of the core a coating ofconducting material of relatively high resistance includingcircumferentially complete elements prior to lthe application of thenon-conductive element, and heating the core by induced effects ofelectrical currents.

13. The method of lheating the insulating A covering of an electricallconducting core having an outer coating o conducting materialimmediately overlying conducting material of relatively lowerresistance, which method comprises passing the insulated conductorthrough a high frequency alternating current magnetic fie d togenerateheat in the conductor which passes radially outwardly from the interiorsurface of the insulating covering.

In testimony whereof, I have signed my name to this specification this20th day of August, 1927.

" FRANK M. POTTER.y

